/*
 * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
 * Copyright (c) 2006 Christian Walter <wolti@sil.at>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * File: $Id: mbtcp.c,v 1.3 2006/12/07 22:10:34 wolti Exp $
 */

/* ----------------------- System includes ----------------------------------*/
#include "stdlib.h"
#include "string.h"

/* ----------------------- Platform includes --------------------------------*/
#include "port.h"

/* ----------------------- Modbus includes ----------------------------------*/
#include "mb.h"
#include "mbconfig.h"
#include "mbtcp.h"
#include "mbframe.h"
#include "mbport.h"

#if MB_TCP_ENABLED > 0

/* ----------------------- Defines ------------------------------------------*/

/* ----------------------- MBAP Header --------------------------------------*/
/*
 *
 * <------------------------ MODBUS TCP/IP ADU(1) ------------------------->
 *              <----------- MODBUS PDU (1') ---------------->
 *  +-----------+---------------+------------------------------------------+
 *  | TID | PID | Length | UID  |Code | Data                               |
 *  +-----------+---------------+------------------------------------------+
 *  |     |     |        |      |
 * (2)   (3)   (4)      (5)    (6)
 *
 * (2)  ... MB_TCP_TID          = 0 (Transaction Identifier - 2 Byte)
 * (3)  ... MB_TCP_PID          = 2 (Protocol Identifier - 2 Byte)
 * (4)  ... MB_TCP_LEN          = 4 (Number of bytes - 2 Byte)
 * (5)  ... MB_TCP_UID          = 6 (Unit Identifier - 1 Byte)
 * (6)  ... MB_TCP_FUNC         = 7 (Modbus Function Code)
 *
 * (1)  ... Modbus TCP/IP Application Data Unit
 * (1') ... Modbus Protocol Data Unit
 */

#define MB_TCP_TID          0
#define MB_TCP_PID          2
#define MB_TCP_LEN          4
#define MB_TCP_UID          6
#define MB_TCP_FUNC         7

#define MB_TCP_PROTOCOL_ID  0   /* 0 = Modbus Protocol */


/* ----------------------- Start implementation -----------------------------*/
eMBErrorCode
eMBTCPDoInit(MBTypeDef* psModbus, USHORT ucTCPPort)
{
    eMBErrorCode    eStatus = MB_ENOERR;

    if( xMBTCPPortInit(psModbus, ucTCPPort) == FALSE )
    {
        eStatus = MB_EPORTERR;
    }
    return eStatus;
}

void
eMBTCPStart( MBTypeDef* psModbus )
{
}

void
eMBTCPStop( MBTypeDef* psModbus )
{
    /* Make sure that no more clients are connected. */
    vMBTCPPortDisable(psModbus);
}

void
eMBTCPClose( MBTypeDef* psModbus )
{
    /* Make sure that no more clients are connected. */
    vMBTCPPortDisable(psModbus);
}

eMBErrorCode
eMBTCPReceive( MBTypeDef* psModbus, UCHAR * pucRcvAddress, UCHAR ** ppucFrame, USHORT * pusLength )
{
	eMBErrorCode    eStatus = MB_EIO;
	USHORT          usPID;
	USHORT          usLength;

	usPID  = psModbus->ucBuf[MB_TCP_PID] << 8U;
	usPID |= psModbus->ucBuf[MB_TCP_PID + 1];
	
	usLength  = psModbus->ucBuf[MB_TCP_LEN] << 8U;
	usLength |= psModbus->ucBuf[MB_TCP_LEN + 1];
	
	if(usPID == MB_TCP_PROTOCOL_ID && psModbus->usRcvBufferPos == (usLength + MB_TCP_UID))
	{
		*ppucFrame = &psModbus->ucBuf[MB_TCP_FUNC];
		*pusLength = psModbus->usRcvBufferPos - MB_TCP_FUNC;

		/* Modbus TCP does not use any addresses. Fake the source address such
		 * that the processing part deals with this frame.
		 */
		*pucRcvAddress = MB_TCP_PSEUDO_ADDRESS;
		
		eStatus = MB_ENOERR;
	}
	
	psModbus->usRcvBufferPos = 0;  /* Reset the buffer. */
	
	return eStatus;
}


eMBErrorCode
eMBTCPSend( MBTypeDef* psModbus, UCHAR _unused, const UCHAR * pucFrame, USHORT usLength )
{
    eMBErrorCode    eStatus = MB_ENOERR;
    UCHAR          *pucMBTCPFrame = ( UCHAR * ) pucFrame - MB_TCP_FUNC;
    USHORT          usTCPLength = usLength + MB_TCP_FUNC;

    /* The MBAP header is already initialized because the caller calls this
     * function with the buffer returned by the previous call. Therefore we
     * only have to update the length in the header. Note that the length
     * header includes the size of the Modbus PDU and the UID Byte. Therefore
     * the length is usLength plus one.
     */
    pucMBTCPFrame[MB_TCP_LEN] = ( usLength + 1 ) >> 8U;
    pucMBTCPFrame[MB_TCP_LEN + 1] = ( usLength + 1 ) & 0xFF;
    if( xMBTCPPortSend( psModbus, pucMBTCPFrame, usTCPLength ) == FALSE )
    {
        eStatus = MB_EIO;
    }
    return eStatus;
}

#endif
